U.S. patent application number 09/833514 was filed with the patent office on 2002-05-16 for titanium dioxide film co-doped with yttrium and erbium and method for procucing the same.
Invention is credited to Chen, San-Yuan, Hsieh, Wen-Feng, Ting, Chu-Chi.
Application Number | 20020056831 09/833514 |
Document ID | / |
Family ID | 21661202 |
Filed Date | 2002-05-16 |
United States Patent
Application |
20020056831 |
Kind Code |
A1 |
Chen, San-Yuan ; et
al. |
May 16, 2002 |
Titanium dioxide film co-doped with yttrium and erbium and method
for procucing the same
Abstract
A doped TiO.sub.2 material for forming a film used in a planar
optical waveguide amplifier. The doped TiO.sub.2 material includes
100 mol % TiO.sub.2 precursor compound, 0.1.about.10 mol % erbium
ion (Er.sup.3+) precursor compound, and 1.about.50 mol % yttrium
ion (Y.sup.3+) precursor compound, thereby forming the doped
TiO.sub.2 film co-doped with erbium and yttrium as an amorphous
structure to achieve the enhancing effect on photoluminescence
properties.
Inventors: |
Chen, San-Yuan; (Hsinchu,
TW) ; Hsieh, Wen-Feng; (Taoyuan City, TW) ;
Ting, Chu-Chi; (Hualien City, TW) |
Correspondence
Address: |
Skjerven Morrill MacPherson, LLP
Suite 700
25 Metro Drive
San Jose
CA
95110
US
|
Family ID: |
21661202 |
Appl. No.: |
09/833514 |
Filed: |
April 11, 2001 |
Current U.S.
Class: |
252/301.4F ;
501/41 |
Current CPC
Class: |
C09K 11/7767
20130101 |
Class at
Publication: |
252/301.40F ;
501/41 |
International
Class: |
C09K 011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2000 |
TW |
089119177 |
Claims
What is claimed is:
1. A doped TiO.sub.2 material for forming a film used in a planar
optical waveguide amplifier, comprising: 100 mol % TiO.sub.2
precursor compound; 0.1.about.10 mol % erbium ion (Er.sup.3+)
precursor compound; and 1.about.50 mol % yttrium ion (Y.sup.3+)
precursor compound; thereby forming said doped TiO.sub.2 film
co-doped with erbium and yttrium as an amorphous structure to
achieve the enhancing effect on photoluminescence properties.
2. The doped TiO.sub.2 material according to claim 1, wherein said
erbium ion (Er.sup.3+) precursor compound is selected from a group
consisting of erbium acetate, erbium carbonate, erbium chloride,
erbium oxalate, erbium nitrate, and erbium isopropoxide.
3. The doped TiO.sub.2 material according to claim 1, wherein said
TiO.sub.2 precursor compound is selected from a group consisting of
titanium isopropoxide, titanium ethoxide, titanium chloride, and
titanium butoxide.
4. The doped TiO.sub.2 material according to claim 1, wherein said
yttrium ion (Y.sup.3+) precursor compound is selected from a group
consisting of yttrium acetate, yttrium carbonate, yttrium chloride,
yttrium oxalate, yttrium nitrate, and yttrium isopropoxide.
5. A method for forming a doped TiO.sub.2 film used in a planar
optical waveguide amplifier, comprising steps of: (a) preparing a
titanium solution having 100 mol % titanium ion (Ti.sup.4+)
precursor compound; (b) preparing a yttrium solution having
1.about.50 mol % yttrium ion (Er.sup.3+) precursor compound; (c)
adding said yttrium solution and an erbium powder with 0.1.about.20
mol % into said titanium solution for forming a sol-gel solution;
and (d) forming said TiO.sub.2 film co-doped with Er.sup.3+ and
Y.sup.3+ by spin-coating and thermal treatment.
6. The method according to claim 5, wherein said step (a) further
comprising steps of: (a1) dissolving titanium isopropoxide in
acetic acid to from a first solution; and (a2) adding
2-methoxyethanol into said first solution.
7. The method according to claim 5, wherein said step (b) further
comprising step of dissolving yttrium acetate in a mixed solution
of methanol and ethylene glycol.
8. The method according to claim 5, wherein said step (d) further
comprising steps of: (d1) spin-coating said sol-gel solution on a
substrate; (d2) thermal treating said substrate at a first specific
temperature for evaporating organic materials thereof; (d3)
repeating steps of spin-coating and thermal treating until said
film reaching a specific thickness; and (d4) thermal treating said
film of said substrate at a second specific temperature for forming
said TiO.sub.2 film co-doped with Er.sup.3+ and Y.sup.3+.
9. The method according to claim 8, wherein said substrate is made
of a material selected from a group consisting quartz, glass, and
silica oxide on silicon (SOS).
10. The method according to claim 8, wherein said first specific
temperature is about 400.degree. C.
11. The method according to claim 8, wherein said second specific
temperature is ranged from 500 to 900.degree. C.
12. The method according to claim 8, wherein said specific
thickness of said film is ranged from 0.1 to 2 .mu.m.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a TiO.sub.2 film co-doped
with yttrium and erbium and a method for producing the yttrium and
erbium co-doped TiO.sub.2 film, and more particularly to an yttrium
and erbium co-doped TiO.sub.2 film used in a planar optical
waveguide amplifier.
BACKGROUND OF THE INVENTION
[0002] Owing to the development of network communication, the
loading of the network information transference is heavier and
heavier. For increasing the data capacity carried by the transform
system, the optical fiber system is applied in the communication
system for satisfying the demand.
[0003] The most important elements of the optical communication
system are light source and optical-guided medium. Owing to the
disclosure of the semiconductor laser, the long effect and stable
light source can be practically applied. At the same time, the
quartz optical fiber having low transmission loss has been
developed. However, during optical fiber transmission, the
transmission loss is inevitable. Thus, it is necessary to set an
amplifier at the intermediate station for a long distance
transmission. Traditionally, the amplifier is used to transfer an
optical signal to an electrical signal, amplify the electrical
signal, transfer the amplified electrical signal to the amplified
optical signal, and transmit out the amplified optical signal.
After the disclosure of the erbium-doped fiber amplifier (EDFA),
however, the optical signal can be directly amplified and
transmitted out.
[0004] During the light transmission, the light source having a
wavelength of 1.53 .mu.m has lower loss and is harmless for human
eyes. When erbium ion is excited by the laser with the wavelength
of 1.48 .mu.m, 0.98 .mu.m or 0.8 .mu.m, the electron located on the
first exciting state will jump back to the ground state and
irradiate an infrared ray with wavelength of 1.53 .mu.m. The
infrared spectra are the light source applied in the current
optical fiber communication.
[0005] Currently, along the development and upgrade of the IC
semiconductor producing technology, the microphoto-electromechanic
system is quickly developed. For the integrated optics devices, the
planar optical amplifier has very important applications.
Furthermore, because the size of the planar optical amplifier is
much smaller than that of the erbium-doped fiber amplifier, the
erbium-doped planar optical waveguide amplifier becomes an
important issue in the integrated optics. Referring to the
erbium-doped planar optical waveguide amplifier, most researches
are focus on either the process improvement or the different host
selection. Generally, the major material of the host is oxide
glass, such as pure silica, soda-lime silicate, phosposilicate and
aluminosilicate glass, because the oxide glass is the major
material for current optical fibers. However, the ceramics material
such as Al.sub.2O.sub.3, TiO.sub.2, Y.sub.2O.sub.3 and LiNbO.sub.4,
or the amorphous silicon material are also used to be the host. The
shape and intensity of erbium-ion fluorescence spectrum are
affected by different host. Furthermore, the fluorescence spectral
characteristics are dependent on the solubility, or the radiative
/non-radiactive relaxation of the erbium ion in the host.
[0006] The cross-relaxation between erbium ions will decrease the
number of excited erbium ion. The cross-relaxation strength between
erbium ions is dependent on the distance between the erbium ions.
That is, while the clustering effect of erbium ions increases, the
photoluminescence efficiency decreases. In addition, a hydroxide
group is a photoluminescence quenching center because the second
harmonic vibration of the hydroxide group can produce resonant
effect with the .about.1.54 .mu.m photoluminescence of erbium ion,
which results in the photoluminescence efficiency decreasing.
Moreover, the up-conversion phenomenon caused by the
cross-relaxation effect between erbium ions will also decrease the
photoluminescence efficiency. Therefore, the photoluminescence
efficiency can be improved by increasing the erbium ion solubility
in host, decreasing the hydroxide group content in host, or
decreasing the probability of the up-conversion, and more
especially by increasing the erbium ion solubility in host.
Generally, the aluminum ion is doped into the silicon oxide
structure for increasing the erbium ion solubility because the
aluminum ion can be a network former and a network modifier to
break the tetrahedron network structure of silicon oxide. Thus, the
number of non-bridging oxygen is increased, which further increases
the erbium ion solubility.
[0007] Another way to increase photoluminescence efficiency is
basically to change host materials because the erbium ion
solubility in host is strongly host-dependent. Thus, a proper host
can increase the erbium ion solubility and further increase the
photoluminescence efficiency. Since TiO.sub.2 host has higher
refraction index (n=2.52 for anatase and n=2.76 for rutile), the
optical modes are increased for enhancing transmission efficiency
and decreasing the bending radii of the optical waveguide. Hence,
the size of optical waveguide device is largely decreased. In
addition, TiO.sub.2 host also has lower phonon energy (<700
cm.sup.-1), so the excited electrons are decreased by non-radiative
losing rate.
[0008] Therefore, Er.sup.3+-doped TiO.sub.2-based film is applied
in the planar optical waveguide amplifier. However, the
photoluminescence properties of Er.sup.3+-doped TiO.sub.2 film
applied in the planar optical waveguide amplifier are not as good
as expectation.
[0009] Therefore, the purpose of the present invention is to
develop a material and a method to deal with the above situations
encountered in the prior art.
SUMMARY OF THE INVENTION
[0010] It is therefore an object of the present invention to
propose an erbium and yttrium co-doped TiO.sub.2 material and a
method for producing the erbium and yttrium co-doped TiO.sub.2 film
used in a planar optical waveguide amplifier for increasing
.about.1.54 .mu.m photoluminescence in emissive intensity.
[0011] It is therefore another object of the present invention to
propose an erbium and yttrium co-doped TiO.sub.2 material and a
method for producing the erbium and yttrium co-doped TiO.sub.2 film
used in a planar optical waveguide amplifier for increasing
.about.1.54 .mu.m photoluminescence in bandwidth.
[0012] It is therefore an additional object of the present
invention to propose an erbium and yttrium co-doped TiO.sub.2
material and a method for producing the erbium and yttrium co-doped
TiO.sub.2 film used in a planar optical waveguide amplifier for
decreasing light scattering.
[0013] It is therefore an additional object of the present
invention to propose an erbium and yttrium co-doped TiO.sub.2
material and a method for producing the erbium and yttrium co-doped
TiO.sub.2 film used in a planar optical waveguide amplifier for
decreasing processing temperature and further reducing the
producing cost.
[0014] According to one aspect of the present invention, there is
provided a doped TiO.sub.2 material for forming a film used in a
planar optical waveguide amplifier. The doped TiO.sub.2 material
includes 100 mol % TiO.sub.2 precursor compound, 0.1.about.10 mol %
erbium ion (Er.sup.3+) precursor compound, and 1.about.50 mol %
yttrium ion (Y.sup.3+) precursor compound, thereby forming the
doped TiO.sub.2 film co-doped with erbium and yttrium as an
amorphous structure to achieve the enhancing effect on
photoluminescence properties.
[0015] Preferably, the erbium ion (Er.sup.3+) precursor compound is
selected from a group consisting of erbium acetate, erbium
carbonate, erbium chloride, erbium oxalate, erbium nitrate, and
erbium isopropoxide.
[0016] Preferably, the TiO.sub.2 precursor compound is selected
from a group consisting of titanium isopropoxide, titanium
ethoxide, titanium chloride, and titanium butoxide.
[0017] Preferably, the yttrium ion (Y.sup.3+) precursor compound is
selected from a group consisting of yttrium acetate, yttrium
carbonate, yttrium chloride, yttrium oxalate, yttrium nitrate, and
yttrium isopropoxide.
[0018] According to another aspect of the present invention, there
is provided a method for forming a doped TiO.sub.2 film used in a
planar optical waveguide amplifier. The method includes steps of
(a) preparing a titanium solution having 100 mol % titanium ion
(Ti.sup.4+) precursor compound, (b) preparing a yttrium solution
having 1.about.50 mol % yttrium ion (Er.sup.3+) precursor compound,
(c) adding the yttrium solution and an erbium powder with
0.1.about.20 mol % into the titanium solution for forming a sol-gel
solution and (d) forming the TiO.sub.2 film co-doped with Er.sup.3+
and Y.sup.3+ by spin-coating and thermal treatment.
[0019] Certainly, the step (a) can further include steps of (a1)
dissolving titanium isopropoxide in acetic acid to from a first
solution and (a2) adding 2-methoxyethanol into the first
solution.
[0020] Certainly, the step (b) can further include step of
dissolving yttrium acetate in a mixed solution of methanol and
ethylene glycol.
[0021] Preferably, the step (d) further includes steps of (d1)
spin-coating the sol-gel solution on a substrate, (d2) thermal
treating the substrate at a first specific temperature for
evaporating organic materials thereof, (d3) repeating steps of
spin-coating and thermal treating until the film reaching a
specific thickness and (d4) thermal treating the film of the
substrate at a second specific temperature for forming the
TiO.sub.2 film co-doped with Er.sup.3+ and Y.sup.3+.
[0022] Certainly, the substrate can be made of a material selected
from a group consisting quartz, glass, and silica oxide on silicon
(SOS).
[0023] Preferably, the first specific temperature is about
400.degree. C. and the second specific temperature is ranged from
500 to 900.degree. C.
[0024] Preferably, the specific thickness of the film is ranged
from 0.1 to 2 .mu.m.
[0025] The present invention may best be understood through the
following description with reference to the accompanying drawings,
in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a plot illustrating X-ray diffraction patterns of
different ratio Er.sub.2O.sub.3: Y.sub.2O.sub.3 : TiO.sub.2 films
treated at different temperature for 1 hour, wherein A, R, and P
represent anatase, rutile, and pyrochlore phase respectively;
[0027] FIG. 2 is a plot illustrating chromatic dispersion curve of
different ratio Er.sub.2O.sub.3: Y.sub.2O.sub.3: TiO.sub.2 films
treated at 700.degree. C. for 1 hour according to the present
invention;
[0028] FIG. 3 is a plot illustrating .about.1.54 .mu.m fluorescence
spectra of different ratio Er.sub.2O.sub.3: Y.sub.2O.sub.3:
TiO.sub.2 films treated at 700.degree. C. for 1 hour according to
the present invention;
[0029] FIG. 4 is a plot illustrating .about.1.54 .mu.m
photoluminescence intensities of the erbium and yttrium co-doped
TiO.sub.2 film treated at 700.degree. C. for 1 hour with different
Er.sub.3+ and Y.sup.3+ concentrations according to the present
invention;
[0030] FIG. 5 is a plot illustrating .about.1.54 .mu.m fluorescence
spectra of the erbium and yttrium co-doped TiO.sub.2 film treated
at 700.degree. C. for 1 hour and the best ratio of erbium and
aluminum co-doped TiO.sub.2 film with the best molar ratio and
treated at 700.degree. C. for 1 hour according to the present
invention; and
[0031] FIG. 6 is a plot illustrating .about.1.54 .mu.m fluorescence
spectra of the erbium and yttrium co-doped TiO.sub.2 film treated
at different temperature ranged from 700 to 900.degree. C. for 1
hour according to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0032] The present invention discloses a TiO.sub.2 host co-doped
with erbium and yttrium to form a TiO.sub.2 film. Owing to the
presence of yttrium ion, the erbium and yttrium co-doped TiO.sub.2
film has 10 times .about.1.54 .mu.m photoluminescence intense
emission and 1.5 times bandwidth of fluorescence spectrum than the
erbium and aluminum co-doped TiO.sub.2 film has, which is thought a
material having excellent photoluminescence property. In addition,
the erbium and yttrium co-doped TiO.sub.2 film requires lower
processing temperature and lower producing cost, so it is a
potential material used in the planar optical waveguide amplifier
of the integrated optics.
[0033] The preparation of the erbium and yttrium co-doped TiO.sub.2
film material is performed by the sol-gel spin coating process.
First, a Er.sup.3+ precursor such as erbium acetate and a Y.sup.3+
precursor such as yttrium acetate are added into a Ti.sup.4+
precursor such as titanium isopropoxide to form a clear solution,
wherein the ratio of Er.sup.3+: Y.sup.3+: Ti.sup.4+ is represented
as X: Y: 1 (mol). Subsequently, the clear solution is applied with
spin coating and thermal treatment to obtain a TiO.sub.2 amorphous
structure co-doped with high concentrations of erbium and
yttrium.
[0034] Referring to the preparation of the sol-gel solution, first,
titanium isopropoxide is dissolved into an acetate solution. After
stirring, 0 2-methoxyethanol is added and is agitated violently. On
the other hand, yttrium acetate is added into a methanol/ethylene
glycol solution with a molar ratio of 3:1. A certain ratio erbium
acetate powder and the above yttrium acetate solution are added
into the titanium isopropoxide solution together. Then, the mixture
solution is agitated for at least 10 hours in order to process
homogenous hydrolysis and condensation reaction among titanium,
erbium and yttrium ions.
[0035] Regarding to the preparation of the film, first of all, the
sol-gel solution is homogenously sputtered on a fused quartz
substrate and spin-coated at a speed of 4000 rprn/30 sec. After
coating, each layer of the film is dried at 150.degree. C. on a hot
plate for evaporating the solvent. Then, the film is treated at
400.degree. C. for 30 minutes at a heating rate of 5.degree. C.
/min to remove the remained organic material of the film. The
spin-coating and annealing steps are repeated until the 0.5 .mu.m
thickness of film is deposited. Then, the film is treated at the
temperature ranged from 600 to 1000.degree. C. for 1 hour at a
heating rate of 10.degree. C./min. Table 1 shows the full width at
half maximum (FWHM) of photoluminescence of film samples at
.about.1.54 .mu.m with different molar ratio of
erbium/yttrium/titanium and erbium/aluminum/silicon, wherein the
Er:Al:Si ratio of samples E and F are formed the best compositions
having the most intense photoluminescence according to Y Zhou's
paper published in Applied Physical Letters, vol.71, p587-589 at
1997. Table 1. The FWHM of photoluminescence in film samples at
.about.1.54 .mu.m of different ratio erbium/yttrium/titanium and
erbium/aluminum/ silicon.
1 Sample A B C D E F Er:Y:Ti 5:0:100 5:10:100 5:30:100 10:30:100 --
-- (mol %) Er:Al:Si -- -- -- -- 0.7:0:100 0.7:8:100 (mol %) FWHM 13
36 75 75 27 50 of PL at .about.1.54 .mu.m (nm)
[0036] FIG. 1 is a plot illustrating X-ray diffraction (XRD)
patterns of different ratio Er.sub.2O.sub.3: Y.sub.2O.sub.3:
TiO.sub.2 films treated at different temperature for 1 hour,
wherein A, R, and P represent anatase, rutile, and pyrochlore phase
respectively. As a pure TiO.sub.2 film (Er.sub.2O.sub.3:
Y.sub.2O.sub.3: TiO.sub.2=0:0:100) is annealed at 700.degree. C.,
an anatase phase 101 is observed. However, with the incorporation
of 5 mol % Er.sup.3+ and 10 mol % Y.sup.3+ into TiO.sub.2 network,
the XRD peak of TiO.sub.2 phase was broadened, indicating the
crystallinity of matrix host becomes poor. Furthermore, as
increasing the doping concentration of Y.sup.3+ to 30 mol %, a weak
broad continuum in the XRD was observed, which is characteristic of
amorphous structure. Thus, while Er.sup.3+ or Y.sup.3+ are added
into TiO.sub.2 network, the crystallinity of TiO.sub.2 (i.e.
anatase phase) will significantly decrease. While the annealing
temperature is 800.degree. C. and the ratio of Er.sub.2O.sub.3:
Y.sub.2O.sub.3: TiO.sub.2 is 5:30:100, a strong preferred peak 222
is observed, demonstrating a pyrochlore phase with the formula of
Er.sub.xY.sub.2-xTi.sub.2O.sub.7 is developed in the
TiO.sub.2-based amorphous structure. While the annealing
temperature is 1000.degree. C., another weak peak 110 is observed,
demonstrating a rutile phase is developed in the TiO.sub.2-based
amorphous structure.
[0037] FIG. 2 is a plot illustrating chromatic dispersion curve of
different ratio Er.sub.2O.sub.3: Y.sub.2O.sub.3: TiO.sub.2 films
treated at 700.degree. C. for 1 hour according to the present
invention. As shown in FIG. 2, a pure TiO.sub.2 film
(Er.sub.2O.sub.3: Y.sub.2O.sub.3: TiO.sub.2=0:0:100) is annealed at
700.degree. C. for 1 hour, the refractive index of the TiO.sub.2
film is 2.28. While the TiO.sub.2 film is co-doped with 5 mol %
Er.sup.3+ and 10 mol % or 30 mol % Y.sup.3+, the refractive indexes
decrease from 2.28 to 2.25 and from 2.28 to 2.13. Thus, according
to the change of Y.sup.3+ concentration, the preparation of an
Er.sup.3+ and Y.sup.3+ co-doped TiO.sub.2 film with flexible
refractive index can be achieved.
[0038] As show in FIG. 3, while the Er.sup.3+ doping concentration
is 5 mol %, once the addition of Y.sup.3+ concentration reaches
above 20 mol %, the intensity increases 3.about.4 times and the
bandwidth increases from 35 nm to 75 nm at the .about.1.54 .mu.m
photoluminescence intensity.
[0039] As shown in FIG. 4, the more Y.sup.3+ is doped into the
host, the stronger the .about.1.54 .mu.m photoluminescence
intensity is, even though the Er.sup.3+ doping concentrations are
different in the host (1, 5, and 10 mol %). In addition, FIG. 5
shows that the Er.sup.3+ and Y.sup.3+ co-doped TiO.sub.2 film
according to a preferred sample of the present invention has 10
times for photoluminescence intensity and 1.5 times for bandwidth
than of the Er.sup.3+ and Al.sup.3+ co-doped silica film with an
optical molar ratio of 0.7:8:100 has. Therefore, the
photoluminescence properties of the Er.sup.3+ and Y.sup.3+ co-doped
TiO.sub.2 film has more intense emission and wider bandwidth while
comparing with that of the pure TiO.sub.2 film or that of the
Er.sup.3+ and Al.sup.3+ co-doped silica film.
[0040] FIG. 6 illustrates the photoluminescence intensity of the
Er.sup.3+ and Y.sup.3+ co-doped TiO.sub.2 film treated at the
different annealing temperatures. The result shows the intensity of
Er.sup.3+ and Y.sup.3+ co-doped TiO.sub.2 film increases with the
increasing temperature when the temperature is not more than
700.degree. C. However, the spectrum of Er.sup.3+ and Y.sup.3+
co-doped TiO.sub.2 film is not significantly changed at this
condition. Once the annealing temperature increases to or over
800.degree. C., the photoluminescence intensity decreases and the
spectrum is divided into several small peaks as shown in FIG.
6.
[0041] The present invention provides an Er.sup.3+ and Y.sup.3+
co-doped TiO.sub.2 film and a method for producing the same. The
TiO.sub.2 film co-doped with 5 mol % Er.sup.3+ and more than 30 mol
% Y.sup.3+ and annealed at 700.degree. C. has the best
photoluminescence properties when the Er.sup.3+ and Y.sup.3+
co-doped TiO.sub.2 film is applied in the planar optical waveguide
amplifier. Therefore, the present invention has the following
advantages:
[0042] (1) The Er.sup.3+ and Y.sup.3+ co-doped TiO.sub.2 film has 4
times for photoluminescence intensity at .about.1.54 .mu.m and 2
times for bandwidth than the Er.sup.3+ doped TiO.sub.2 film
has.
[0043] (2) When comparing with a typical Er.sup.3+ and Al.sup.3+
co-doped silica film used in the planar optical waveguide
amplifier, the Er.sup.3+ and Y.sup.3+ co-doped TiO.sub.2 film has
10 times for photoluminescence intensity at .about.1.54 .mu.m, 1.5
times for bandwidth, and 1.3 times for refraction.
[0044] Therefore, an amplifier device produced by the Er.sup.3+ and
Y.sup.3+ co-doped TiO.sub.2 film has higher efficiency and smaller
size.
[0045] (3) The Er.sup.3+ and Y.sup.3+ co-doped TiO.sub.2 film has
an amorphous structure, so the light scattering can be
decreased.
[0046] (4) The temperature of thermal treatment is about
700.degree. C. that is much lower than the typical processing
temperature for the Er.sup.3+ and Al.sup.3+ co-doped silica film,
so the present invention can decrease largely the processing
temperature and further reduce the producing cost. In addition, the
lower temperature is more properly applied in the planar optical
waveguide amplifier because the typical quartz substrate cannot
endure higher temperature in the process.
[0047] While the invention has been described in terms of what are
presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention need not to
be limited to the disclosed embodiment. On the contrary, it is
intended to cover various modifications and similar arrangements
included within the spirit and scope of the appended claims which
are to be accorded with the broadest interpretation so as to
encompass all such modifications and similar structures.
* * * * *